Xylan is one of the major polysaccharides in cellulosic biomass. There are four Arabidopsis REDUCED WALL ACETYLATION (RWA) genes which are shown to be involved in the acetylation of xylan during secondary wall biosynthesis. See Lee et al., “The Four Arabidopsis REDUCED WALL ACETYLATION Genes are Expressed in Secondary Wall-Containing Cells and Required for the Acetylation of Xylan”, Plant Cell Physiol (2011) 52 (8): 1289-1301.